The present invention relates to safety closures for containers such as those used to hold medicines, pesticides, poisons and other potentially harmful substances. More particularly, this invention relates to a two-piece safety closure assembly that is simple in construction, relatively inexpensive to manufacture, yet highly effective for its intended purpose.
A number of cases have been reported in recent years where small children have opened medicine bottles and the like and swallowed the contents, causing severe personal injury or death. Consequently, much effort has been expended to develop closures for these containers which cannot readily be opened by small children, but which, on the other hand, may be opened with relative ease by adults.
Many of the safety closures that have been developed for use on threaded containers have employed a pair of closure members that must be manipulated in some way so that they will cooperate in the opening of the closure. Some of these closures have required an intermeshing of sets of teeth on the closure members which are engaged by pushing the members together as the assembly is turned to remove it from the container. Such closures are disclosed in Scuderi's U.S. Pat. Nos. 3,733,000, 3,924,770 and 3,946,890. These closures are generally comprised of plastic members because of the relative ease with which teeth may be molded in plastic. It is possible to press or form teeth in a metal safety closure member, but the dimensional accuracy, precise definition and small size generally required for such teeth render such a process quite difficult and generally uneconomical.
There are certain advantages, however, which would inhere in a closure assembly having an outer member of sheet metal. Such an assembly could be made with a smaller diameter than an all-plastic assembly, because a plastic overcap would require a thicker skirt than a metal overcap in order to provide the requisite strength. A metal overcap also offers printing advantages over a similar overcap of plastic. Generally, plastic overcaps are printed, if at all, by a stamping method. This method is generally not appropriate for printing small characters of high legibility or for printing on a non-planar surface, such as the curved skirt of a generally cylindrical overcap. A metal overcap, on the other hand, may be printed before forming by offset lithography. This method allows small, precise characters to be printed on a planar metal blank before the blank is formed into a generally cylindrical overcap.
For the aforementioned reasons, it would be advantageous if a closure assembly employing a metal overcap and avoiding the problems inherent in providing teeth in such an overcap could be developed. One such assembly is described in U.S. Pat. No. 3,097,756 of Dorsey. As shown in FIGS. 17-30 of the Dorsey patent, a two-piece safety closure assembly may be provided with an inner cap having a series of ratchet teeth and an outer shell having a series of depending resilient tongues struck from the top wall of the shell. However, these structures are not alone sufficient to provide the safety feature of the closure, and a tool, such as a coin, must be employed to lock the inner cap and outer shell together in order that the closure may be removed from the container. Thus, although the closure assembly of Dorsey avoids the problem of providing teeth in a metal overcap, it requires the employment of a tool in order to remove the closure from the container.
An improved safety closure assembly having a metal overcap which avoids the problem of providing teeth of small dimensions in metal and which may be operated independent of any external tools is therefore desired.